UK-based The Register reported that the feature added in Firefox 13 that displays thumbnails of previous sessions when clicking on the new thumbnail tab can contain secure violations such as showing bank information, email subject lines, and anything else that was on your most recently closed browser tabs. A fix is promised in future versions, but if you don't want to wait we'll show you how to block this feature now.

Since Firefox is highly customizable by users putting a stop to this possible security breach isn't difficult. Computing weblog GHacks notes that you can access the configuration settings by typing about:config in your browser's address bar, finding the preference named browser.newtabpage.enabled, and then changing the value from true to false. This will disable the thumbnail new tab page and instead display a blank page.

Ghacks has two other ways to get around this security issue; for more information visit the source link below.